The word "受约束" is formed by the character 受, meaning "to receive" or "to undergo", followed by 约束, a compound meaning "constraint" where 约 signifies "to bind" or "agree" and 束 means "to bind" or "restrain". Together, 受 passively receives the action of 约束, resulting in a literal sense of "to receive binding" or "to undergo restriction", conveying the meaning of being constrained or limited.